1. Field of the Invention
This invention relates to a nove high-density chromium oxide-base ceramic material, and more particularly to a chromium oxide-base ceramic material suitable for use as a sliding material or abrasion resistant mechanical parts in a wide temperature range from normal to high temperatures.
2. Description of the Prior Art
Cr.sub.2 O.sub.3 has been known as a raw material for good sliding materials with a small coefficient of friction over a wide temperature range from normal to high temperatures, including Cr.sub.2 O.sub.3 -Cr cermets and the like. It is also known in the art that Cr.sub.3 C.sub.2 -Ni cermets have similar properties.
However, the above-mentioned cermets with a metal content become unusable at temperatures of about 1000.degree. C. due to softening of the metal component in a considerable degree. Consequently, there has been a strong demand for development of a material which can be used in a broad temperature range covering from normal temperature to temperatures higher than 1000.degree. C.
The ceramic material which is applicable as a sliding material or as a abrasion resistant mechanical part in a wide temperature range from normal to high temperature is required to have the following properties: a small coefficient of friction in that temperature range; less abrasive wear; and high deflection resistance.
Especially, since he service life of a sliding material is shortened by seizure on a contacting material, it's coefficient of friction should be as small as possible. On the other hand, there occurs a phenomenon of abrasive wear entailing a sort of fine cracks generally referred to as "chipping." In case of a ceramic material, it is important to prevent such chipping since it greatly restricts the range of applications of the material. To prevent chipping, it is necessary to secure greater deflection resistance. Greater the deflection resistance, greater becomes the toughness of the material.
Further, above-mentioned chipping is brought about by tensile force, and the resistance to such tensile force is greatly influenced by the pores which are contained in the ceramic material. Accordingly, in order to prevent chipping, the ceramic material should be free of pores, namely, should have a high density.